The structure, occurrence and biological activity of ellagitannins: a general review

Abstract

The present paper deals with the structure, occurrence and biological activity of ellagitannins. Ellagitannins belong to the class of hydrolysable tannins, they are esters of hexahydroxydiphenoic acid and monosaccharide (most commonly glucose). Ellagitannins are slowly hydrolysed in the digestive tract, releasing the ellagic acid molecule. Their chemical structure determines physical and chemical properties and biological activity. Ellagitannins occur naturally in some fruits (pomegranate, strawberry, blackberry, raspberry), nuts (walnuts, almonds), and seeds. They form a diverse group of bioactive polyphenols with anti-infl ammatory, anticancer, antioxidant and antimicrobial (antibacterial, antifungal and antiviral) activity. Furthermore, they improve the health of blood vessels. The paper discusses the metabolism and bioavailability of ellagitannins and ellagic acid. Ellagitannins are metabolized in the gastrointestinal tract by intestinal microbiota. They are stable in the stomach and undergo neither hydrolysis to free ellagic acid nor degradation. In turn, ellagic acid can be absorbed in the stomach. This paper shows the role of cancer cell lines in the studies of ellagitannins and ellagic acid metabolism. The biological activity of these compounds is broad and thus the focus is on their antimicrobial, anti-infl ammatory and antitumor properties. Ellagitannins exhibit antimicrobial activity against fungi, viruses, and importantly, bacteria, including antibiotic-resistant strains such as methicillinresistant Staphylococcus aureus.

Bioactive components of pomegranate fruit and their transformation by fermentation processes

“…Being compounds of a complex structure, they readily undergo chemical reactions, such as transformation or isomerization. They are hydrolyzed in the alimentary tract by intestinal microflora to a sugar molecule and molecules of ellagic and gallic acids [23,24]. Metabolism of these compounds is initiated by the decomposition of the ellagitannin to sugar and a molecule of ellagic acid, which is further transformed to urolithins in the small and large intestines.…”

“…Urolithins are absorbed to the portal hepatic circulation, where they may serve the role of hormone analogs. Bioavailability of ellagitannins is dependent on the location, at which these molecules are absorbed, the efficiency of their release from nutrients during digestion, their concentration and interactions with other components found in the medium [24]. It needs to be stressed that absorbability of these compounds in the human organism is limited.…”

Fructus phyllanthi tannin fraction induces apoptosis and inhibits migration and invasion of human lung squamous carcinoma cells in vitro via MAPK/MMP pathways

“…Fructus phyllanthi, the dried ripened fruit of Phyllanthus emblica L and a traditional Tibetan medicine, has been used clinically for thousands of years in the Tibetan area. Its active extracts have been shown to possess several pharmacologic activities, including anti-tumor, anti-inflammatory, anti-bacterial, and anti-viral activities [9][10][11] . Fructus phyllanthi primarily contains tannins, phenolic compounds, phyllembelic acid, rutin, curcuminoids, and emblicol [12] .…”

Use of Phytoestrogens for the Treatment of Psychiatric Symptoms Associated with Menopause Transition

“…Clinical and preclinical studies have shown that pomegranate has anti-oxidant [77], anti-inlammatory, antitumorigenic, anti-microbial [78], anti-obesity [79], anti-nociceptive [80], neuroprotective [81] and antidepressant-like properties [82][83][84]. Interestingly, most of the health beneits of pomegranate are atributed to its high content of polyphenols, which represents the 26-30% of the total weight of the fruit [85].…”

“…Therefore, on diferent portions of the small and large intestine, ellagitannins are transformed by bacterial metabolism to dibenzopyranone compounds called urolithins. These compounds have recently demonstrated to possess estrogenic activity on in-vitro assays; this particularity makes pomegranate an excellent source of phytoestrogens [16,22,78,89]. Under this premise, some research groups have sought its therapeutic potential for the treatment of symptoms in menopause.…”